Textile yarn cores, i.e., yarn carriers or bobbins, are widely used in the textile industry for winding and supporting yarn packages. In the package forming process, a moving yarn line is strung up on a rapidly rotating empty core. Typically, one or more of the initial strands of yarn are introduced into a starting groove cut into the surface of one end of the core so that the yarns are thereby secured onto the tube and subsequently wound onto the core in a uniform pattern.
In building a yarn package onto a rapidly rotating core, typically a small number of initial yarn windings are provided at one end of the core spaced from the main yarn package. This initial yarn grouping is referred to in the art as a "transfer bunch" or "transfer tail." The transfer tail is segregated from the primary body of the yarn package so that an end of the yarn wound onto the core can be readily found at a later point in time. For example, the transfer tail can be subsequently tied to the yarn end of another yarn package to allow a series of yarn packages to be connected so that when the thread of the first package runs out during a manufacturing process, unwinding of the thread on the second package immediately begins.
One problem encountered during and after winding of the yarn onto the core, particularly when the yarn core is covered with a smooth exterior paper covering, is the slippage of the transfer bunch or tail off of, or along the core. Several prior techniques of securing the transfer tail to the core have been proposed. In one such technique, a narrow continuous groove or ring is formed circumferentially about one end of the exterior peripheral surface of the yarn core. The yarn is held in contact with the groove of a rotating yarn core until several yarn windings are retained therein to secure the transfer bunch.
In another technique, the circumferential exterior peripheral surface of the core is roughened by abrading or grinding the paper surface. This results in the surface filaments or fibers being raised from the body of the core and thus providing a continuous roughened area which will provide friction or retention of the yarn.
U.S. Pat. No. 2,569,094 to Dunlap discloses another textile core for supporting yarn packages against slippage on the core. The core is disclosed as having knob-like raised configurations or bosses spaced circumferentially at either end of the core. The spaced bosses provide a configured pattern at the ends of the core adapted to anchor the end loops against slippage. The spaced bosses may be formed on the core either by forming them in a semi-circular paper blank and applying the blank to the core after it is formed or by embossing the raised portions in the core body after it is formed. This structure has not, however, achieved widespread commercial acceptance.
These and other core configurations can provide some amount of anti-slip properties to the exterior of a core to prevent slippage of a transfer tail during and after winding processes. However, there can be problems associated with these configurations. For example, typically cores having a circumferential groove around one end thereof exhibit decreased core structural integrity. This is especially noticeable in the sidewalls of the core, which can exhibit reduced strength.
Similarly, processes used to form cores having a roughened or abraded surfaces can also result in a weakened sidewall structure. For example, the core must be maintained at a specific angle while in contact with the abrading surface. If the angle position is moved even slightly outside of the beginning plane, then the abrading device can cut into the surface of the cone, resulting in an uneven, weakened sidewall. In addition, it is often desirable to provide visible indicia on the surface of the core, designating, for example, the source or type of yarn. Printing such indicia is typically difficult to achieve on a roughened surface.
The past decade has evidenced continually increasing speeds for winding of yarns onto textile cores. As the winding speeds have increased, the need to form transfer tails at increasing winding speeds has resulted in increasing slippage of transfer tails either off of, or along the core, resulting in increasing numbers of defective yarn packages. However the increasing yarn winding speeds have also increased the need for yarn cores of high wall strength.